Determining the absolute geophysical location of a streamer is of prime importance, among other applications, in marine seismic data acquisition. In order to properly use marine seismic reflection data it is critical that the absolute geophysical location of the receiving hydrophone arrays of a towed streamer be accurately known. Methods currently practiced for determining the absolute location of a streamer require
(1) knowledge of the absolute location of the towing vessel,
(2) knowledge of the magnetic heading of the streamer at several points along the streamer, PA0 (3) knowledge of the relative location of reference signal detecting devices at several points along the streamer, and PA0 (4) knowledge of the absolute location of reference signal source(s) either relative to the seismic vessel or relative to a fixed absolute coordinate system.
Since according to the prior art it is necessary to know the absolute location of the reference signal source(s), the reference signal source(s) are either placed near the boat (thus losing triangulation accuracy for the more distant portions of the streamer) or are towed in the near vicinity of a second marine vessel, the second vessel also being equipped with a maritime navigation system (thus considerably increasing the expense of the seismic survey).
It is a feature of the present invention to accurately determine the absolute geophysical location of a streamer in an improved manner wherein independent a priori knowledge of the absolute location of reference signal source(s) (or alternately of reference signal detectors) is not required, thus eliminating a great cause of expense and error.
It is a further feature of the present invention to recognize that streamer location can be absolutely determined in an improved manner by breaking such determination into three steps, each of the steps being accurately achieved by utilizing one characteristically appropriate type of field measurement.